1,721,336 research outputs found
A framework for studying social complexity
No full textSocial complexity has been one of the recent emerging topics in the study of animal and human societies, but the concept remains both poorly defined and understood. In this paper, I critically review definitions and studies of social complexity in invertebrate and vertebrate societies, arguing that the concept is being used inconsistently in studies of vertebrate sociality. Group size and cohesion define one cornerstone of social complexity, but the nature and patterning of social interactions contribute more to interspecific variation in social complexity in species with individual recognition and repeated interactions. Humans provide the only example where many other unique criteria are used, and they are the only species for which intraspecific variation in social complexity has been studied in detail. While there is agreement that complex patterns emerge at the group level as a result of simple interactions and as a result of cognitive abilities, there is consensus neither on their relative importance nor on the role of specific cognitive abilities in different lineages. Moreover, aspects of reproduction and parental care have also been invoked to characterize levels of social complexity, so that no single comprehensive measure is readily available. Because even fundamental components of social complexity are difficult to compare across studies and species because of inconsistent definitions and operationalization of key social traits, I define and characterize social organization, social structure, mating system, and care system as distinct components of a social system. Based on this framework, I outline how different aspects of the evolution of social complexity are being studied and suggest questions for future research
Evidence for a male sex pheromone in a primate?
No full textPheromones mediate a wide range of functions across the animal kingdom [1], and such chemosensory communication is especially widespread among mammals [2]. In a recent paper in Current Biology, Shirasu, Ito et al. [3] describe the results of a series of chemical and behavioral studies that identified three aldehyde odors released from the wrist gland of ring-tailed lemurs (Lemur catta) that could represent the first identified sex pheromones in male primates. Observations of a captive group and controlled presentations of isolated male scent samples showed captive female lemurs sniffing antebrachial scent marks longer on average during the breeding season. Comparison of the chemical profiles of antebrachial secretions between breeding- and non-breeding-season samples revealed three aldehydes putatively responsible for the female response, the concentration of one of these subsequently shown to increase following testosterone injection of one male. Average sniffing duration of two females increased slightly with increasing concentrations of two of the three aldehydes in one experiment, and so did the response of seven other females to swabs with mixtures of the three compounds, compared to individually presented aldehydes. From these results, the authors conclude that "it is conceivable that the identified C12 and C14 aldehydes are putative sex pheromones that aid male-female interactions among lemurs." Here, I argue that, in fact, more data are needed to determine whether antebrachial marking and these substances are actually involved in mediating the attractiveness of males to females during the breeding season. My specific concerns pertain to several aspects of the methods that produce ambiguous results and conclusions that are too strong, especially when considering the broader context of lemur biology
Causes and Consequences of Life-History Variation Among Strepsirhine Primates
No full textThe aims of this study were to examine potential causes of variation in fundamental life-history traits and to illuminate their consequences for social behavior in the most primitive living primates. Specifically, I reexamined the claim that life histories of strepsirhine primates (lemurs and lorises) are metabolically constrained and tested the hypothesis that female social dominance, a behavioral idiosyncracy of Malagasy strepsirhines, is the result of unusually high energetic maternal investment in reproduction. I collected data on body mass, brain mass, metabolic rate, and fetal and postnatal litter growth rates for 21 lemur and 13 loris species to examine the relationship between maternal investment and the other variables after controlling for allometric and phylogenetic effects. I found that evolutionary changes in fetal growth rates, relative litter mass, and postnatal growth rates were associated with evolutionary changes in maternal mass but that neither brain size nor metabolic rate were independently correlated with variables reflecting maternal investment. Evolutionary changes in all three variables reflecting maternal investment were positively correlated with one another, however, indicating that they are coadapted, only broadly constrained by body size, and unconstrained by brain size and metabolic rate. Lemurs and lorises were found to have similar postnatal litter growth rates; which reflect the bulk of maternal reproductive investment, indicating that the energetic costs of reproduction did not figure prominently in the evolution of female dominance. The suggested unusual energetic stress of reproducing lemur females is further refuted by qualitative comparison with higher primates and other mammals. Thus, strepsirhine life histories are not narrowly constrained by nonadaptive forces and have no direct consequences for social relations between adult males and females
Determinants of Primate Social Organization: Comparative Evidence and New Insights from Malagasy Lemurs
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Verhaltensbiologie
No full textFressen und Nicht-gefressen-Werden, Paarungspartner finden und Junge erfolgreich aufziehen – diese grundlegenden Prinzipien der Verhaltensbiologie werden in dem Lehrbuch übersichtlich und anhand aktueller Beispiele dargestellt. Neben dem Thema Verhaltensbiologie als integrative Disziplin liegt der inhaltliche Schwerpunkt bei Fragen der Evolution des Verhaltens, der Anpassung, der Verhaltensökologie, Soziobiologie und Evolutionsbiologie. Die Neuauflage wurde um einige eindrucksvolle Fotos ergänzt, das Kapitel zum Sozialverhalten erweitert.4., korrigierte Auflag
Nests, tree holes and the evolution of primate life histories
No full textIn contrast to the majority of primates, many prosimians, some New World monkeys, and the great apes rest in tree holes or self‐constructed nests during their inactive periods. The goal of this comparative study was to examine possible functions of this interspecific variation. Information on resting behavior, maternal behavior, and basic life‐history traits was gleaned from the literature and mapped onto a phylogenetic tree of primates for various comparative tests. Parsimony‐based reconstructions revealed that only the use of nests or tree holes as shelters for young infants can be unequivocally reconstructed for various higher taxa, suggesting that it is functionally different from the use of shelters by adults (who may be accompanied by infants). Further reconstructions revealed that the ancestral primate was most likely nocturnal and solitary and produced a single infant that was initially left in a shelter and later carried orally to a parking place in the vegetation—a combination of traits exhibited by many living galagos. Evolutionary losses of the use of nests were concentrated among diurnal and nonsolitary taxa and weakly associated with evolutionary increases in body size. Thus, protective functions of nests or tree holes used by prosimians are either secondary or there are alternative ways of obtaining protection. Because the evolution of larger litters was significantly associated with the presence of shelters, the presence of relatively altricial young among prosimians best explains the use of nests and tree holes, which are in most but not all cases also used by adults. These shelters therefore play an integral part in the life‐history strategies of primitive primates and their ancestors and evolved secondarily among anthropoids for other purposes
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